Stephen Hawking is considered one of the world's leading figures in cosmology and theoretical physics. Nevertheless, he dedicates a disproportionate amount of time to the study of what seems to be science fiction: time travel, to be exact. In his words, time travel is possible because it does not require a change in space, but only a change in speed. "Time flows like a river," he argues, "but it flows at different speeds in different places and under different conditions. This is the key to time travel." For example, it is known that time slows down as one gets closer to heavy bodies in space. These giant masses draw matter towards them and cause time dilation.

Time dilation was proven when clocks aboard a space shuttle in orbit were found to run more slowly than clocks on earth. Precise synchronization of the time in space and on earth is essential, because any discrepancy can cause the GPS controlling the shuttle's movement to malfunction, and put the shuttle off course by at least 10 kilometers each day. Sophisticated computers take into account the shuttle’s speed and position to recalibrate the clocks aboard the spaceship, to keep them aligned with clocks on earth.

According to Einstein’s theory of relativity, high speed travel also causes time to slow down.  The faster one travels, the slower the clock runs compared to clocks at rest. For example, let's say someone travels around the earth in a high speed train at close to the speed of light, circling the earth seven times a second. If he spends a week on that train and then gets off, he will find a very different world than the one he left -- a hundred earth years will have passed during his one week of travel.

On a spiritual plane, we are familiar with the phenomenon of time speeding up or slowing down depending on conditions. When we are engaged in enjoyable activities, time seems to fly; when engaged in dull or painful activities, time drags.

Heavy matter can cause time to slow down in its vicinity. Similarly, the more bound we are to the physical world, the more slowly time moves for us. By investing in more spiritual pursuits – Torah study, prayer, mitzvot – we lift ourselves above the boundaries of time and space. Time is a precious commodity. When we use it properly, we can pack a great deal into a short interval of time.

In practical terms, we must fill our time with as many mitzvot as possible, for there is not much time left. At any moment Moshiach will reveal himself. The time of our Redemption has already arrived, as the Lubavitcher Rebbe predicted. We must intensify our activities in the time we have left, to bring the complete Redemption one moment sooner.

Prof. Yirmiyahu Branover is chairman of the Center of Magnetohydrodynamic Studies and Training at Ben-Gurion University.